Hi Roman if $map is your map object than the lines below would set the extent of the reference map:
$map->reference->set('minx',-180)
$map->reference->set('miny',-180)
$map->reference->set('maxx',180)
$map->reference->set('maxy',180)
(The numbers -180, 180 are just examples)
I hope it helps.
Erik
